Electromagnetic switching device

ABSTRACT

An electromagnetic switching device, such as a wire spring relay, includes a coil having one leg of a substantially U-shaped core inserted into a central bore of the coil. An L-shaped armature is hinged for movement to the core so that pole faces of the armature mate with associated pole faces of the core when an operating potential is applied to the coil. A plurality of groups of parallel wires are embedded in and extend from a plastic support block which is attached to one leg of the core. The ends of the wires are spaced apart and extend through openings in a card which is attached to the movable armature and a restoring spring. When the switching device is operated, the armature is moved so that the pole faces thereof mate with the associated pole faces of the core whereby the card is moved against the biasing of the restoring spring to bring together selected wires of the parallel groups of wires to facilitate electrical connections in external circuits connected to the opposite ends of the selected wires.

United States Patent [72] Inventors Robert F. Klose Blacklick; Virgil L.Marsh, Reynoldsburg, Ohio [21] Appl. No. 849,683 [22] Filed Aug. 13,1969 [45] Patented Apr. 6, 1971 [73] Assignee Western Electric Company,Incorporated New York, N.Y.

[54] ELECTROMAGNETIC SWITCHING DEVICE 3 Claims, 7 Drawing Figs.

[52] US. Cl 335/135 [51} Int. Cl H0lh 50/00 [50] Field of Search335/135, 133, 279, 281, 277, 249

[56] References Cited UNITED STATES PATENTS 1,980,393 11/1934 Evans335/249 2,715,199 8/1955 Bogue... 335/249 3,290,629 12/1966 Jeanne335/133 3,479.627 11/1969 Underwood 335/277 Primary ExaminerHaroldBroome Att0rneysH. J. Winegar, R. P. Miller and Don P, Bush ABSTRACT: Anelectromagnetic switching device, such as a wire spring relay, includesa coil having one leg of a substantially U-shaped core inserted into acentral bore of the coil. An L-shaped armature is hinged for movement tothe core so that pole faces of the armature mate with associated polefaces of the core when an operating potential is applied to the coil. Aplurality of groups of parallel wires are embedded in and extend from aplastic support block which is attached to one leg of the core. The endsof the wires are spaced apart and extend through openings in a cardwhich is attached to the movable armature and a restoring spring, Whenthe switching device is operated, the armature is moved so that the polefaces thereof mate with the associated pole faces of the core wherebythe card is moved against the biasing of the restoring spring to bringtogether selected wires of the parallel groups of wires to facilitateelectrical connections in external circuits connected to the oppositeends of the selected wires.

Patented April 6, 1971 3,573,685

lA/VENTORS R F A1055 1/ L. MARSH ATTORNEY ELECTROMAGNETIC SWITCHINGDEVICE BACKGROUND OF THE INVENTION 1. Field of the Invention Thisinvention relates to an electromagnetic switching device andparticularly to miniature devices having plated elements of a magneticcircuit of the device which are mated during operation of the device.

2. Description of the Prior Art In the manufacture of some types ofelectromagnetic switching devices, such as a wire spring relay of thetype disclosed in US. Pat. No. 3,290,629, which issued to A. L. .leanneon Dec. 6, I966, a magnetizable core is positioned within a central boreof a coil with pole faces of the core being positioned to engageassociated pole faces of an armature. When an operating potential isapplied to the coil, a magnetic circuit is established to draw the polefaces of the armature into engagement with the associated pole faces ofthe core. The mechanical movement of the armature is utilized tomanually close contacts of circuits which are not necessarilyelectrically associated with the coil of the switching device.

In order to reduce undesirable corrosion of and provide wear resistancefor the core and armature, the core and armature are plated withcorrosion resistant and hard wear materials, such as nickel andchromium, respectively, which enhance the operating properties of theelectromagnetic switching device. However, a buildup of nickel andchromium occurs on the mating pole faces'of the core and the armature insuch a manner that, when the armature is drawn toward the core, the polefaces do not mate sufficiently to retain the switching device in theoperated state when a normal level of holding current is passed throughthe coil. In addition, certain types of magnetic latching switchingdevices depend upon the retention properties of the core and armaturefor maintaining a sufficient magnetic field for holding the pole facesin the mated engagement after the operating potential has beencompletely removed from the coil. The buildup of the plating materialusually occurs at the ends of the pole faces so that the pole faces havea bowed appearance. When an operating potential is applied to the coilof the switching device and the armature is moved toward the core, theareas of the plated buildup at the opposite ends of the pole faces mateleaving the remaining center portions of the mating pole faces spacedsubstantially apart thereby creating an airgap and a deficiency in themagnetic circuit of the switching device.

SUMMARY OF THE INVENTION It is, therefore, an object of this inventionto provide a new and improved electromagnetic switching device.

Another object of this invention is the provision of a new and improvedelectromagnetic switching device having plated magnetic circuit elementswhich prevent corrosion and provide wear surfaces of the elements andpermit mating of the pole faces of the elements to complete the magneticcircuit.

Still another object of this invention is the provision of a new andimproved electromagnet switching device wherein mating pole faces of acore and armature of the device are designed so that plated buildupareas of the mating pole faces are offset so that the mating pole facesmay be positioned sufficiently close to each other to maintain themagnetic circuit in a state sufficient to retain the switching device inthe operated condition.

An electromagnetic device illustrating certain principles of theinvention may include a coil having a core of magnetic materialpositioned within an opening and extending from one end thereof. Anarmature made of magnetic material is hinged to the core for movementrelative thereto and is formed with at least one pole face which mateswith an associated pole face of the core when a magnetic field isdeveloped by the coil upon the application of an operating potentialthereto. The core and the armature then function as a linked flux pathfor the magnetic field. At least one of the pole faces is bowed alongits length which results in an airgap between the arma- LII ture and thecore. To reduce the undesirable effects of the airgap, the pole faces ofthe core and the armature are formed with dissimilar length dimensionsto permit the bowed pole face to move sufficiently close to the otherpole face and thereby provide a sufficient flux path of magneticmaterial.

The core and the armature are plated with noncorrosive and wearresistant materials, such as nickel and chromium, respectively, and thepole faces are designed so that plated buildup areas on the pole facesdo not mate when the pole faces are drawn together thereby minimizingany airgap deficiencies in the linked flux path and permittingsufficient mating engagement of the associated pole faces to retain theflux path in the linked state.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of thepresent invention will be apparent from the following detaileddescription when considered in conjunction with the accompanyingdrawings in which:

FIG. I is an elevational view of a wire spring relay;

FIG. 2 is a sectional view taken along line 2-2 of FIG. 1 showingportions of wires of the wire spring relay;

FIG. 3 is a partial perspective view showing mating portions of the wirespring relay;

FIG. 4 is a partial end view showing mated pole faces of an armature anda core of the wire spring relay;

FIG. 5 is a partial perspective view showing a modified armature usedwith the wire spring relay in accordance with certain principles of theinvention, and

FIGS. 6 and 7 are partial end views showing mated pole faces of themodified armature and the core of the wire spring relay.

DETAILED DESCRIPTION Referring now to FIG. I, there is illustrated anelectromagnetic switching device, such as a wire spring relay,designated generally by the reference numeral II, which is of the typedisclosed in the aforementioned US. Pat. No. 3,290,629. The wire springrelay II includes a contact assembly, designated generally by thereference numeral 12, and a motor assembly, designated generally by thereference numeral I3. The motor assembly 13 includes a coil 14 wound ona bobbin, designated generally by the reference numeral 16. One leg 17of a substantially U-shaped core, designated generally by the referencenumeral 18, which is made of a magnetic material, is inserted into acentral bore 19 of the bobbin 16. The free end of the leg I7 of the coreI8 extends from one end of the bobbin 16 and is formed with a beveledpole face 21. Another leg 22 of the core 118 is parallel to the leg 17and is spaced therefrom so that the leg 22 extends along an adjacentportion of the periphery of the coil 14. The free end of the leg 22 ofthe core I8 is formed with a bevel pole face 23.

The motor assembly 13 also includes a substantially L- shaped armature,designated generally by the reference numeral 24, which is made of amagnetic material and is formed with legs 25 and 26. The free ends ofthe legs 25 and 26 are formed with beveled pole faces 27 and 28,respectively. A hinge strap 29 extends between and is attached toportions of the core 18 and the armature 24 adjacent to the pole faces23 and 28, respectively, so that the armature is mounted for hingedmovement with respect to the core. Therefore, the core 18 and thearmature 24 form a two element magnetic circuit for concentrating themagnetic flux developed when an operating potential is applied to thecoil 14.

The contact portion 12 includes a pair of spaced, molded blocks 30 and31 having intermediate portions of a plurality of parallel, spaced wiresprings 32-32 (FIG. 2) and 33-33 (FIG. 2), respectively, embeddedtherein with remaining portions of the wire springs extending fromopposite sides of the blocks. Another molded block 34 is positionedbetween the molded blocks 30 and 31 and has molded therein intermediateportions of a plurality of parallel, spaced wires 36-36 (FIG. 2)

which extend from opposite sides of the block. One free end of each ofthe wires 36-36 is assembled with an associated contact block 37. Thewire springs 32-32 and 33-33, the wires 36-36 and the contact blocks37-37 are composed of suitable conductive materials. Outer plasticmembers 38 and 39 are positioned adjacent to the blocks 30 and 31,respectively, and are formed with inwardly projecting portions 41 and42, respectively. The projecting portions 41 and 42 engage intermediateportions of the wires 32-32 and 33-33, respectively, to urge adjacentfree end portions of the wire springs normally into engagement withassociated portions of the contact blocks 37-37.

Referring to FIGS. 1 and 2, there is illustrated a U-shaped clamp,designated generally by the reference numeral 43, which is positionedover the stacked blocks 30, 31, 34 and the outer members 38 and 39 andis formed with a pair of tabs 44-44 which latch onto the leg 22 of thecore 18 to secure the contact assembly 12 with the motor assembly 13.

Referring again to FIG. 1, a card, designated generally by the referencenumeral 47, is provided with a pair of actuator surfaces 48 and 49 andis positioned so that the free ends of the wire springs 32-32 can engagethe surface 48 and the free ends of the wire springs 33-33 can engagethe surface 49. The upper end of the card 47 is attached to one end of arestoring spring 51 which extends from and is attached to the outermember 38 so that the card is urged normally upwardly. When the card 47is urged normally upwardly, the surface 48 of the card engages and urgesthe free ends of the wires 32-32 upwardly and out of engagement with theassociated contact blocks 37-37. In addition, the free ends of the wiresprings 33-33 are permitted to engage adjacent portions of associatedcontact blocks 37-37 when the card 47 is urged normally upwardly.

The lower end of the card 47 is connected to one end of a bracket 52,the other end of which is secured to the hinge 29 and to one surface ofthe armature 24. When an operating potential is applied to the coil 14,a magnetic flux is developed within the core 18 and normally urges thearmature 24 toward the core so that the mating pairs of pole faces 21and 27, and 23 and 28 are mated in flush and overlapping engagement toestablish a concentrated path in the form of a closed loop circuit forthe magnetic flux. As the armature 24 is moved toward the core 18, thecard 47 is moved downwardly against the biasing action of the restoringspring 51 whereby the surface 49 engages the free ends of the wiresprings 33-33 and facilitates the movement of the free ends of the wiresprings out of engagement with the associated contact blocks 37-37. Inaddition, the surface 48 of the card 47 is moved sufficiently downwardlyto permit the free ends of the wire springs 32-32 to engage theassociated contact blocks 37-37. In this manner, external electricalcircuits, which can be connected to the opposite ends of the wiresprings 32-32 and 33-33 and the wires 36-36, can be controlled byoperation of the wire spring relay 1] to provide necessary switchingfunctions for the external circuits.

In one type of the miniature wire spring relay 11, after the closed loopcircuit for the magnetic flux has been completed by the mating of thepole faces 21 and 27, and 23, and 28, the amount of current requirednormally through the coil 14 to hold the armature 24 in the closed loop,magnetic circuit is less than the amount of current required toestablish the circuit. Therefore, the current level can be reduced to aholding level so that power requirements are lowered. In a magneticlatching type of the wire spring relay 11, the retentivity properties ofthe core 18 and the armature 24 are sufficient to hold the pole faces 21and 27 and 23 and 28, in mating engagement after the operating potentialhas been removed completely from the coil 14. In this manner, the relay11 is in a latched condition and the card 47 is held in the downwardposition until a reverse potential is applied to the coil 14.

Referring now to FIG 3, there is illustrated the armature 24 having astructure previously used with the wire spring relay 11. The armature 24is normally drawn adjacent to the core 18 to provide the closed loopmagnetic flux path. The leg 17 of the core 18 is smaller in width thanthe leg 22 of the core to facilitate the insertion of the leg 17 throughthe opening 19 of the bobbin 16. To accommodate the reduced width of theleg 17, the leg 25 of the armature 24 is of the same width as the leg 17so that the pole faces 21 and 27 of the legs 17 and 25, respectively,should be in completely overlapping and flush engagement. The leg 26 ofthe armature 24 is of the same width as the leg 22 of the core 18 sothat the pole faces 23 and 28, of the legs 22 and 26, respectively,should mate in complete flush and overlapping engagement.

In order to enhance the operation of the motor assembly 13 (FIG. I) andto reduce the possibility of corrosion to and provide hard wear surfacesfor the core 18 and the armature 24, the core and the armature areplated with corrosion resistant and wear resistant materials, such asnickel and chromium, respectively. As a result of the nickel andchromium plating operation, a substantial buildup of nickel and chromiumoccurs at opposite ends of each of the pole faces 21, 23, 27 and 28(FIG. 1). When the motor assembly 13 is operated and the armature 24 isdrawn toward the core 18, the mating pole faces 21 and 27, 23 and 28 areprevented from moving into complete overlapping and flush engagement dueto the nickel and chromium buildup at opposite ends of the mating polefaces.

Referring now to FIG. 4, there is illustrated portions of the core 18and the armature 24 with the pole faces 23 and 28,

respectively, in mating engagement. However, due to the.

nickel and chromium buildup on opposite ends on each of the pole faces23 and 28, a substantial airgap 56 appears centrally between the matedpole faces. The same type of condition appears between the pole faces 21and 27 (FIG. 1). The presence of the sizable airgaps in the magneticflux path reduces the concentration of the flux within the circuit andnecessitates a higher level of current to hold the armature 24 in aposition adjacent to the core 18 so that the card 47 (FIG. 1) may beretained in the downward position. Therefore, the subsequent supplyingof a normal level of holding current to the coil 14 is not sufficient tohold the armature 24 in the position to hold the card 47 in the downwardposition and the relay 11 will not function properly.

When attempts are made to remove the nickel and chromium buildup on theopposite ends of the pole faces 21, 23, 27 and 28 by various processes,such as an abrasive technique, the structure of the plated material isfrequently disturbed. Also, it is difficult to remove accuratelysufficient portions of the material buildup without exposing theoriginal surface of the core 18 and armature 24 whereby corrosion andwear of the exposed unplated portions of the surface of the pole faces21, 23, 27 and 28 will subsequently occur and interfere with the normaldesired operation of the wire spring relay 11. In order to overcome theundesirable aspects of the buildup of the nickel and chromium at theopposite ends of the pole faces 21, 23, 27 and 28, the length dimensionsof the pole faces 27 and 28 of the armature 24 are modified asillustrated in FIG. 5 so that these pole faces are no longer the samedimensions as the mating pole faces 21 and 23, respectively, of the core18.

As illustrated in FIG. 5, the width of a leg of a modified armature 124is substantially wider that the leg 25 (FIG. 3) of the original armature24 so that a pole face 127 at the free end of the leg 125 is longer thanthe pole face 27 of the armature 24. In addition, the width of a leg 126of the modified armature 124 is substantially less than the width of theleg 26 (FIG. 3) of the original armature 24 so that a pole face 128 atthe free end of the leg 126 is shorter in length than the pole face 28of the armature 24.

Referring now to FIG. 6, there is illustrated the end of the leg 22 withthe pole face 23 and the end of the leg 126 with the mating pole face128. The width of the leg 126 is substantially less than the width ofthe leg 22 so that the pole face 128 is permitted to move relativelyclose to the pole face 23 when the armature 124 is moved adjacent to thecore 18. Even though an airgap 156 exists between the pole face 23 and128,

the size of the airgap is substantially less than the airgap 56 (FIG. 4)thereby minimizing the effect of the airgap in the magnetic circuit andconcentrating substantially the magnetic flux between the leg 22 and theleg 126 of the core 18 and the armature 124, respectively.

Referring now to FIG. 7, since the width of the leg 125 of the modifiedarmature 124 is substantially greater than the width of the leg 17 ofthe core 18, the mating pole face 127 of the modified armature ispermitted to move sufficiently close to the pole face 21 so that themagnetic flux is concentrated sufficiently for the relay 11 to functionproperly even though a small airgap 57 exists between the pole faces.

With the structure of the modified armature 124, the corrosion and wearresistant materials can be plated onto the modified armature and thecore 18 without any subsequent need for disturbing the plated materialto maintain the relay 11 in an operable condition. The structure of themodified armature 124 then permits sufiicient closing of the loop of themagnetic flux path so that the wire spring relay ll can operate with anormal level of holding current after the relay has been operated. Ifthe relay 11 is a magnetic latching type, the magnetic circuit loop isclosed sufficiently to permit the relay to remain in a latched conditionafter the relay has been operated.

We claim:

1. An electromagnetic switching device, which comprises:

a coil;

two flux concentrating elements which are alignable to form aconcentrated path for magnetic flux;

a first of said elements being arranged in a position adjacent to thecoil to concentrate magnetic flux developed when an operating potentialis applied to the coil;

a second of said elements being arranged to be moved toward the first ofsaid elements when the operating potential is applied to the coil andhaving at least one mating portion thereof which engages an associatedmating portion of the first of said elements to provide normally analignment of the two flux concentrating elements;

the mating portion of at least one of said elements being plated withmaterial which results in a buildup of plated material on the matingportion of the at least one of said elements, whereby the mating portionis bowed along the length thereof which results in an airgap beingformed between the mating portions of the two elements when the portionof the second of said elements is moved into engagement with the matingportion of the first of said elements; and

the bowed mating portion of the one element having a length dimensiondifferent than the length dimension of the mating portion of the otherelement to pennit the mating portions of the elements to movesufficiently close to each other so that any airgap caused by the bowedportion of the one element is insufficient to prevent the substantialengagement of the mating portions and alignement of the elements to formthe concentrated path for the magnetic flux.

2. An electromagnetic switching device, which comprises:

a coil having an opening;

a core made of a magnetic material and extending through the opening ofthe coil to form a flux path of magnetic material for a magnetic fielddeveloped by the coil when an operating potential is applied to thecoil;

the core being formed with at least one pole face at one end thereof ian armature made of a magnetic material and hinged to the core formovement relative thereto;

the armature formed with at least one pole face at one end thereof whichis arranged to mate with the associated pole face of the core when themagnetic field isdeveloped to increase the flux path of magneticmaterial;

at least one of the pole faces being plated with material which resultsin a buildu of plated material on the pole face whereby the pole ace lSbowed along the length thereof; and

the pole faces of the core and the armature having dissimilar lengthdimensions to permit the bowed pole face to move sufficiently close tothe other pole face so that any airgap between the pole faces isinsufficient to create an undesirable deficiency in the flux path formedby the mated core and armature.

3. An electromagnetic switching device, which comprises:

a coil having a central opening;

a core made of a magnetic material and having a first leg extendingthrough the opening of the coil and a second leg fon'ned integrally withthe first leg and extending parallel to the first leg adjacent to theouter surface of the coil to form a first portion of a flux path ofmagnetic material for a magnetic field developed by the coil when anoperating potential is applied to the coil;

the core being formed with a pole face at each end thereof;

an armature made of a magnetic material and being hinged to one leg ofthe core for movement relative thereto to form a second portion of aflux path of magnetic material for the magnetic field;

the armature being formed with a pole face at each end thereof which arearranged to mate with associated ones of the pole faces of the core whenthe magnetic field is developed to form a substantially closed loop fluxpath of magnetic material for the developed magnetic field;

the core and the armature being plated whereby a buildup of platingmaterial occurs on opposite ends of at least one of the pole facesthereof which results in the pole faces being bowed along the lengththereof; and

the bowed pole faces of the core and the armature having dissimilarlength dimensions to permit the mating bowed pole faces to movesufficiently close together so that any airgap between the bowed polefaces is insufficient tocreate an undesirable deficiency in the fluxpath formed by the mated core and armature.

1. An electromagnetic switching device, which comprises: a coil; twoflux concentrating elements which are alignable to form a concentratedpath for magnetic flux; a first of said elements being arranged in aposition adjacent to the coil to concentrate magnetic flux developedwhen an operating potential is applied to the coil; a second of saidelements being arranged to be moved toward the first of said elementswhen the operating potential is applied to the coil and having at leastone mating portion thereof which engages an associated mating portion ofthe first of said elements to provide normally an alignment of the twoflux concentrating elements; the mating portion of at least one of saidelements being plated with material which results in a buildup of platedmaterial on the mating portion of the at least one of said elements,whereby the mating portion is bowed along the length thereof whichresults in an airgap being formed between the mating portions of the twoelements when the portion of the second of said elements is moved intoengagement with the mating portion of the first of said elements; andthe bowed mating portion of the one element having a length dimensiondifferent than the length dimension of the mating portion of the otherelement to permit the mating portions of the elements to movesufficiently close to each other so that any airgap caused by the bowedportion of the one element is insufficient to prevent the substantialengagement of the mating portions and alignement of the elements to formthe concentrated path for the magnetic flux.
 2. An electromagneticswitching device, which comprises: a coil having an opening; a core madeof a magnetic material and extending through the opening of the coil toform a flux path of magnetic material for a magnetic field developed bythe coil when an operating potential is applied to the coil; the corebeing formed with at least one pole face at one end thereof; an armaturemade of a magnetic material and hinged to the core for movement relativethereto; the armature formed with at least one pole face at one endthereof which is arranged to mate with the associated pole face of thecore when the magnetic field is developed to increase the flux path ofmagnetic material; at least one of the pole faces being plated withmaterial which results in a buildup of plated material on the pole facewhereby the pole face is bowed along the length thereof; and the polefaces of the core and the armature having dissimilar length dimensionsto permit the bowed pole face to move sufficiently close to the otherpole face so that any airgap between the pole faces is insufficient tocreate an undesirable deficiency in the flux path formed by the matedcore and armature.
 3. An electromagnetic switching device, whichcomprises: a coil having a central opening; a core made of a magneticmaterial and having a first leg extending through the opening of thecoil and a second leg formed integrally with the first leg and extendingparallel to the first leg adjacent to the outer surface of the coil toform a first portion of a flux path of magnetic material for a magneticfield developed by the coil when an operating potential is applied tothe coil; the core being formed with a pole face at each end thereof; anarmature made of a magnetic material and being hinged to one leg of thecore for movement relative thereto to form a second portion of a fluxpath of magnetic material for the magnetic field; the armature beingformed with a pole face at each end thereof which are arranged to matewith associated ones of the pole faces of the core when the magneticfield is developed to form a substantially closed loop flux path ofmagnetic material for the developed magnetic field; the core and thearmature being plated whereby a buildup of plating material occurs onopposite ends of at least one of the pole faces thereof which results inthe pole faces being bowed along the length thereof; and the bowed polefaces of the core and the armature having dissimilar length dimensionsto permit the mating bowed pole faces to move sufficiently closetogether so that any airgap between the bowed pole faces is insufficIentto create an undesirable deficiency in the flux path formed by the matedcore and armature.